Fixed Partial Denture Connectors PDF

# Fixed Partial Denture Connectors ## **DR. YASSER M. ALY** Lecturer of Fixed Prosthodontics, Faculty of Dentistry Alexandria University ## **Components of FPD** * Connector * Pontic * Retainer * Abutment Preparation * Abutment * Edentulous Ridge ## **Definition** Connectors are those parts o...

# Fixed Partial Denture Connectors ## **DR. YASSER M. ALY** Lecturer of Fixed Prosthodontics, Faculty of Dentistry Alexandria University ## **Components of FPD** * Connector * Pontic * Retainer * Abutment Preparation * Abutment * Edentulous Ridge ## **Definition** Connectors are those parts of a fixed partial denture (FPD) that join the individual retainers and pontics together. ## **Connectors are classified into:** 1. **Rigid Connectors** * Cast * Soldered * Laser Welded 2. **Non-rigid Connectors (Attachments)** * Precision * Semi-precision ## **Rigid Connectors** ### **A) Cast Connectors** These connectors are shaped in wax as part of multiunit wax pattern, then cast as one piece with the FPD itself (single-piece casting). **Advantages** * Convenient and minimize the steps in FPD fabrication. * Less armamentarium. * Less time consuming. **Disadvantages:** * Distortion in multiunit wax pattern fabrication. * Restricted to simple restorations. ## **Connector Design** The size, shape and position of connectors influence the success of the prosthetic appliance. Therefore, connectors should be: * **Sufficiently large to prevent distortion or fracture during function (Length Vs Width).** * **Provide adequate access for oral hygiene measures at tissue surface of connector (embrasure space).** * **Optimally placed as not to interfere with esthetics.** * **Highly polished at the tissue surface.** * **Have an elliptical shape in a proximal view while, a concave shape in a buccal or lingual view.** Optimal connectors are easy to clean, strong, and aesthetically pleasing. ### **B) Soldered Connectors (Joints)** The metal components are joined by a filler metal *“SOLDER”*, which is fused to each of the parts being joined. The melting temperature of this intermediate metal alloy must be lower than that of the parent metal. * **Soldering:** the filler metal has a melting point below 450° C. * **Rigid connections in dentistry are generally fabricated above 450° C.** Connectors to be soldered are waxed to final shape and then sectioned with a thin ribbon saw. The surfaces to be joined should be flat and parallel. An even gap width of 0.25 mm is recommended. Cleanliness of the surfaces is very important to allow good wetting by the solder alloy.  **Straight cut across interproximal connector**  **Diagonal cut across pontic** Flat cut, minimal clean distance 0.13 to 0.3  **Thin ribbon saw**    **Fig 26-20 Pencil marks are used as an antiflux on the occlusal surface of the castings.**  **Fig 26-21 Flux is placed in the solder joint area.**  **Fig 26-23 The flame is directed against the investment from all sides until it glows if the flame is left in one place for a few seconds.**  **Fig 26-24 Solder is placed into the lingual notch.**  **Fig 26-79 The retainer-pontic segment is seated last.**  **Fig 26-80 A tapered pin is driven through the pontic, the wing, and back out through the pontic.** **Requirements of solder alloys** * **Lower fusion temperature than parent alloy** * **High tarnish and corrosion resistance** * **Flow freely during the soldering procedure** Lower fineness gold solders are more fluid and so used to join castings. Higher fineness solders tend to flow less freely and are used for building up contacts. * **High strength comparable to parent alloy** * **Non pitting** * **Color matching to parent alloy** Solder should possess a fusion temperature about 60 degrees C (100-150 F) below that of the metal being soldered. ## **Factors Affecting Success Of Soldering Procedure** 1. Gap distance between the assembled units (0.25mm). 2. Solder alloy selection (Pre-ceramic or post-ceramic). 3. Soldering flux and antiflux (Borax glass/Graphite). 4. Soldering investment (Gypsum + Phosphate bonded). 5. Mode of heat application (Torch or Oven). 6. Soldering technique (Free hand soldering tech. Vs Investment soldering tech.) ## **Solder Flux** * It is applied on a metal surface to remove oxides or prevent their formation. * The solder will be then free to wet and spread over the clean metal surface. ## **Types of fluxes** * **For gold alloys:** borax glass because of its affinity to copper oxides. * **For base metal alloys:** fluoride fluxes to dissolve stable oxides of chromium, cobalt and nickel. ## **Solder Antiflux** * Used to limit the spreading of the solder alloy. * It is placed on the casting before flux application. e.g: Graphite pencil Iron oxide (rouge) ## **A Solder May Be Used For:** 1. Joining the components of FPD. 2. Building up proximal contacts. 3. Repairing casting voids or broken part. ## **C. Welding Connectors** It may be spot welding by use of electric current. Laser welding: pulsed Nd YAG laser with high power. Laser welding is an autogenous welding technique making use of the strong instantaneous thermal effect of laser beam concentrated on a minute spot. Wax patterns are constructed and cast in the usual manner but contact areas are modified to be flat with minimal space between parts. Welding is then performed on the master cast directly as minimal heat is produced. * **Its maximum penetration depth is 2.5 mm.** * **Can be used on ceramic or resin veneer without distortion.** ## **Non-Rigid Connectors** An attachment is a connector consisting of two or more parts. One part is connected to a root, tooth or implant and the other part to a prosthesis. There are certain exceptions where some attachments have only one manufactured part, and the dentist or technician makes the other part. Attachments fall into two main categories, Precision and Semi-precision. ## **Attachment Applications:** 1. **Fixed Partial Dentures (FPD)** 2. **Removable partial dentures (RPD)** 3. **Over dentures** 4. **Implant-supported restorations** 5. **Maxillofacial prosthetics** Non-rigid connectors are mainly used to relieve stresses or to accommodate mal-aligned FPD abutment teeth. ## **Cases In Which A Non-Rigid Connector Should Be Used:** * **Pier abutments** * **Tilted Molar abutments** * **Tooth-Implant supported FPD** * **Free-end saddle cases as a connection between FPD and RPD**   • Among those used are : * Dove tail connectors (key and ways) or (tenon - Mortise) * Loop connectors * Split pontic * Cross pin and wing connectors. ## **The Precision Attachments (Prefabricated Types)** Their components are machined in special alloys under precise tolerances. Its accurate fitting interlocking device is used to fix removable restoration to the natural teeth. Most precision attachments are made of platinum-palladium alloys that can withstand the high temperature associated with casting of metal ceramic alloys.  ## **The Female Attachment Is Incorporated In A Wax Pattern, And The Assembly Is Invested. After Wax Elimination. The Restoration Is Cast Directly Onto The Attachment.**  ## **The Semi-Precision Attachments (Laboratory-Made)** They are fabricated by direct casting of wax, plastic or refractory patterns. They are considered "semi-precision" since in their fabrication they are subjected to inconsistent water/powder ratios, burn out temperatures and other variables. The resulting components, therefore, vary to a small degree. Their main advantages are economy, ease of fabrication, and ability to cast in a wide choice of alloys without the problem of coefficiency differences between the cast alloy and the machined alloy. ## **A Semi-Precision Attachment Can Be Fabricated In Lab. By Either:** 1. Using prefabricated plastic female and male components. 2. Using a precision milling machine to cut the female(key way) portion into the wax pattern, then the male (key) portion is fabricated using autopolymerizing acrylic resin and attached to the pontic and finally casted.  ## **Factors Considered When Selecting An Attachment:** For proper attachment selection, five factors should be evaluated: **location, function, retention, available space** and **cost.** **I. Location:** * Intracoronal * Extracoronal * Radicular / Intraradicular stud type * Bar type * Cross-pin and wing * Split pontic attachment **II. Function:** Tooth supported restorations are considered solid, whereas tooth and tissue supported restorations are considered resilient. Resilient attachments may allow movements ranging from just the vertical plane to universal resiliency in any plane (Stress breaker). **III. Retention:** * **Frictional:** Offers resistance and retention as the two surfaces are in intimate contact with each other. * **Mechanical:** Retention due to engagement of undercut. * **Frictional and Mechanical:** Combines both above features. * **Magnetic** * **Screwed** **IV. Available Space:** * Vertical * Faciolingual * Mesiodistal **V. Cost:** Precision Vs Semi-precision attachments *** ## **Thanks for your Attention**